The present invention relates to susceptor packaging materials and packages constructed therefrom for use in heating foods in a microwave oven. The invention is an improvement in U.S. Pat. No. 4,914,266 to Parks, and is related to the invention disclosed in U.S. patent application Ser. No. 574.736 filed Aug. 30, 1990, now U.S. Pat. No. 5,132,144. Parks, who is a coinventor of the present invention. The construction of the present invention represents a further refinement in the prior inventions of Parks and produces a level of performance not achieved by the prior inventions.
Current commercial microwave susceptor technology utilizes vapor deposited metallized films of aluminum on film that are laminated to paper or paperboard substrates. The metallized film technology is not readily adaptable to the application of susceptors in selected patterns nor can it be readily manipulated to control the level of heat generated in any one part of the susceptor substrate. The prior U.S. patent and pending patent application of Parks each address these problems and establish the viability of printed susceptors using known printing methods and equipment including gravure and flexography. The performance of containers prepared from the susceptor packaging materials of the Parks patent and patent application has been found to be comparable to metallized aluminum susceptors in the generation of heat and provides the flexibility of controlling both the location and amount of heat produced by the susceptor. However, during the development of those inventions, it was discovered that the substrate on which the susceptor was printed could become degraded during cooking from the generation of excess heat by the susceptor. The generation of excess heat increased the danger of fire or excessive smoking that needed to be minimized to provide a commercially acceptable product. Accordingly, the present invention was developed to address these problems and to provide a commercially acceptable susceptor packaging material of greater refinement, predictability and performance.